So, DP's DB and his wife have just had a baby. DP rings DB on Thursday to ask if we can round to see the baby for the first time on Friday. DB says no, they'll come to ours Sunday. DP says Sunday is absolutely no good because Sylvie is working all day (twelve and a half hour shift). DB says they will try to come on Saturday. Saturday comes and goes, no sign of them. Late Saturday evening DP gets a text saying they're coming on Sunday. Neither of us is happy about this, but DP is all like I can't get into a confrontation with them when they've just had a baby and refuses to talk to his DB about it. So I go off to work on Sunday and they and DP's mum come round with the baby, and DP gives them the presents I carefully selected, bought and wrapped months ago, and I'm left out of the whole thing!
But it's not only this. I've never been able to build much of a relationship with them. DP and DB are not really close, they're quite different people. DP: bookish, sensitive, university-educated, teacher, teetotal. DB: laddish, a drinker, left school at 16, works in a factory. We've never seen him and his wife loads and when we do it is an effort for both of us.
There have been a few things they've done that have pissed me off. For example, DB is our DS's godfather (DP's choice) but he has never taken much interest in him.
DP lent DB £500 when I was pregnant with DS, which we couldn't really afford, and DB has never paid us that money back, though they have been on several holidays since and are now in the process of buying their council house 
. (We, on the other hand, are finally going on our first holiday for three years this summer, as we haven't been able to afford it until now). DP refuses to ask for the money back and says we should just write it off. (It went towards paying debts).
They never say thank you for birthday and Christmas presents, for themselves or for their kids. Ever.
One time it was DP's birthday and we invited people round at four in the afternoon for a little party. DB didn't want to come at 4pm (he didn't have other plans, he just didn't want to come) so he turned up at 10 in the morning instead, with wife and two kids in tow! My friend from overseas was coming to stay that evening and I was rushing round trying to get the house clean for that and the official party happening in the afternoon, and somewhat stressed, so I stayed upstairs cleaning for most of the time they were here. After that DB complained to DP about me being "unfriendly", and came round less (his wife didn't actually come round again until this Sunday when they brought the baby over, which basically means she didn't come round for three years).
Another time we went round to drop a present off for their DD. We were in a rush (my mum had given us a lift up there and was waiting in the car outside) so it was just a very quick visit, but it led to another complaint about my supposed unfriendliness because apparently I didn't say hello or goodbye (I don't remember this - I'm sure I must've acknowledged them with a nod or a wave).
And one time, and this is a little thing but it pissed me off no end and now is my chance to get it off my chest (!), DB's DD threw up all over my settee and when he asked me for a cloth to clean it up with I told him to use the old cloth under the cupboard under the kitchen sink but instead he helped himself to a new one out of the packet, and it wasn't just any old cloth but a fancy M&S one, and of course it had to be thrown away afterwards so it was a complete waste, and what made it even more irritating was that the DD had obviously thrown up because she'd been allowed to stuff herself stupid with crisps before they came over, it wasn't like she was ill or anything...!!!!
I've never said anything to them about any of these things (though with the cleaning cloth thing I really wish I had!!). One, I'm quite shy, and two, I think it's DP's place to deal with his family. I was brought up to be polite to people I don't know very well and that is exactly what I've tried to do every time I've seen them. My only crime, as I see it, has been my shyness. But apparently they now feel justified in leaving me out of big family occasions.