Now that DS is here (4 months old), SIL has decided that, since we have said there will probably be no siblings, she has to start having children immediately so that her children can be close in age to DS. I feel like that's silly, and I really do not want to be in any way, shape, or form, even remotely responsible for SIL possibly having children earlier than she's ready to just because she thinks it's important for her kids to have a cousin close in age (obviously I have no control over what she does, and if she wants children now, that's fine, but don't tell me it's because of how old my baby is in comparison!).
So the reason to have a baby is to give your child a playmate? Not computing! Just because they are cousins, that doesn't make it an automatic BFF playmate confidant. They may not get along or they may be as different as night and day. I don't understand why people assume blood relations automatically mean they will be close. I love my cousins because they are family, but there is some I would not even want to be in the same room with because they are obnoxious (and they may feel that way about me). I am lucky that, even though there is 6 years between us, I am super close with my sister but I have friends that don't even speak to their siblings but once or twice a year. I would never question anyone's family planning choices and I preferred people staying out of my uterus.
Also, like, maybe earthgirl will be too busy to set up very many play dates with the cousin! That's a heck of an assumption.
And it's assigning a really big responsibility
It reminds me a bit of my ILs buying a "country home" and saying, "the kids can swim in the pool." I flat-out told them, "Do not buy this house under the assumption that we will be spending very much time there. We will visit at most two weekends--that's all we'll be able to do. We have busy lives, and our Saturdays are full of stuff like birthday parties, family outings, chores, etc. So don't put the responsibility on us, we refuse to take it."
They bought it anyway, and indeed, we were only free to go up about twice a year. A couple of years ago, my FIL said something wistfully about "we'd thought maybe the kids would spend more time," and implying that their main purpose for buying the place hadn't been realized so it had been wasted effort and money. And I said, gently, "You do remember that I told you we wouldn't be able to come up very often, right?"
So I'd be really annoyed if SIL was assuming that I'd be arranging my life to create playdates for the cousins. I guess the kids would have someone their age at family gatherings, which might make them less boring. Or *more* annoying, if they end up not getting along.