I think the most important thing is healthy eating.  Eliminate, or keep to absolute minimum, cookies, potatoe chips, ice cream, etc.  Absolutely no soda.   Snacks should be carrots, celery and in season fruit.  Growing kids do eat a lot, but emphasizing vegetables and staying away from red meat should be healthier and better for your budget.  

I think it is a stage. My son is 12, and in the last month there has not been enough food in the world to satisfy him! Son is small, only 71lbs and 10th percentile for height and not even on the curve for weight, so we let him eat. We just guide towards healthy choices: Not hungry enough for a salad before your chips? Then guess you are not really hungry! But he eats more than me and my 6ft 3, 220lb firefighter DH combined. It is insane!

Most preteens and teenagers snack and then can also pack away a full size meal.

I would suggest grocery shopping in bulk as over the long haul it can save on costs, for DH.

Since DH doesnt seem concerned if there are special snacks have DH pick those up for the days of visitation only and don’t stock them full time.

Teen and preteen boys often are HUGE eaters. Separate finances and let your husband buy groceries for his kids if you don't want to take on that expense. I hope he's eating that frequently because he's active and growing, and that he's not just a junk food junkie who plays video games all day and will be headed for obesity.

Unfortunately yes, teens eat all the time.  

My 15 dd routine

7.15am breakfast 

11am Snack at breaktime 

1.30pm Lunchtime

3.30 pm after school snack

5.30pm Dinner

9pm pre bed snack/supper

And there is nothing of her.  

So yes teens eat alot, but that doesn't mean that she can only eat 'junk' for snack's she (and my younger 2) have the choice of 1 sweet, 1 savoury and 1 fruit.

Just because they are hungry doesn't mean they get free reign to eat junk.

It is quite a shocking thing to see boys go from "normal" to absolutely voracious vacuum cleansers that hoover up every morsel of food in sight - and still be hungry two hours later. Trust me, when it happened to me, the very question I asked was: IS THIS NORMAL??!!

My son was also around 12 when I swear he went from "normal" to feeding frenzy... And the reason I noticed it, was because it was summer holidays, my son was home as was his cousin (same age and staying at my home) and my son's two best friends were there every day... Four 12 / 13 year olds who were nothing but constant huge mouths... Where it normally took 2 weeks to fill my wheelie bin and recycling bin, these constant chompers would do it in less than a week... So yes, at some point there is this exponential leap where they are constantly hungry. (Part of it was that they were quite active: cycling, swimming, hiking, every day,  but that only accounted for a small portion of where the calories were going... These boys were just food black holes!)

A normal day would be 3 set meals (breakfast, lunch and dinner, with 3 snack times after meals - the final "snack" being a sweet course after dinner. They would eat from around 7 in the morning when they got up to around 9 at night. Because they only went to bed well after midnight, I would stop meals at 9, but allow them to free range on the fruit bowl - usually bananas or apples, if they were still hungry and needed ANOTHER snack.

My best advice to you is not so much how much they are eating, but WHAT they are eating. Speaking to both a dietician and paediatritian, I was advised to cut out as much of the sucrose (sugar)  as I could, and make sure the boys got high fat food (avocados, full fat yoghart, nuts, whole eggs,  etc.). Also to give them lots of vegetables as prepared snacks. Crisps, chocolates, soda was to be cut to minimums and to switch to rye bread or whole grain breads rather than white. If they were going to eat like ravenous animals, it was best to make sure the food was nutritious and kept them filled for longer to stabilse blood sugar (glucose)  and insulin levels... 

So yes, they get snacks, but it would be full fat / double cream yoghart and fruit, rather than crips. Instead of a sarmie, make a vegetable bake or a large salad with home made dressing and something as basic as tinned tuna for protein. Cost wise it works out very similar but it is healthier options that leave them fuller for longer and they arent loading up on chemically enhanced crap. A simple change would be switching from PB and jelly/jam on white to peanut butter, cheese or banana on whole wheat or rye... which would cut their sugar intake or spike and later sugar low. Where I live a litre of milk is the exact same price as a litre of coca cola...  Guess what they got to drink?  (Not the coca-cola!)   .

So yes, you can say the kids are not my problem, I am not paying any money for what is going down their throats, or you can help with what they are eating by making changes, which should not impact your budget by more than 10-15% by making clever  changes... Or you can help DH make those changes, rather than increasing what you spending where  you food bill is likely to double and the boys are still hungry even though they are wolfing down unhealthy choices....

If you want some help or advice on how to modify or change what they eat, let me know and I will  give you some tips on how to do it. The "what" they eat, makes a huge difference on "how much" they eat through simple changes.
 

12 is kind of young to start the voracious eating, but yes, boys going through puberty eat a ton. If he's not overweight, than he's probably heading into puberty and a growth spurt.

If he is overweight, then this is not puberty, it's something else entirely.

But either way, it's not your responsibility to deal with.  Depending on how you guys handle money, ask DH to put in more for groceries since SS is eating so much.

Yes normal. SD12 (almost 13) before she hits a growth spurt is starving all the time. We keep healthy things around and let her know she can help herself. Which she doesn't do, but that's not my issue. She will eat huge meals...double what I do most times. DH had to learn to make bigger meals too. We kept running out of food. ShesS pretty active and thin so no worries here.