BIL (DHs brother) is a lot a bit of a twat. Won't go into chapter and verse of why, but he's a mysoginistic, rude, ungrateful, selfish and all round unpleasant person.
He never buys cards or presents for birthdays/Xmas, not even for DH and DD, or his sister and nieces/nephews. Even though his mum lost her own mum a few days before Mothers Day, he didn't get her a Mother's Day card (things like that mean a lot to MIL).
The only time we've ever got cards and presents is when he's had a GF and they've clearly made the effort on his behalf. Because most of them have run for the hills before long, we haven't received cards or presents in about 3 years (DD is only 2.5 so has never had one). He has a DD, who we always buy cards and presents for, and last few years BIL has got a card but no present. At Xmas, we opened gifts at MILS and we'd got DNiece (his DD) a tricycle. She loves it and rode it all day, but BIL "couldn't be bothered putting it in the car" so left it. It's still at MILS 
It's not a cash flow problem with him - he works 40 hours a week a £20ph. His rent is only £400pcm and he only pays £40 a week child maintenance, plus regular bills (before anyone asks, he has told us this before when he's moaning about paying "too much" child maintenance to his ex). Plus he smokes weed like it's going out of fashion, God knows how much that costs. So he's not skint, he's just selfish and thoughtless.
Anyway, he is 35 next week - which DH says is a 'big birthday' 
- and DH wants us to get him a card and £50 voucher like we did when his sister turned 35.
I've said he can do what he wants, but it's not coming out our joint money, it can come out his own. I don't see why I should fork out for someone who has ignored us and DD for years in the present stakes.
DH says I'm being mean and didn't appreciate my joke that drug dealers don't do vouchers and that's it's only fair as SIL got the same - but SIL is actually a nice person who makes the effort with us all.
AIBU to begrudge BIL and make DH pay for all the voucher - I don't suppose BIL will ever know (or care) that this is how we paid for it. I just get sick of everyone pandering to him when he shows no appreciation back.