This is long...but I need some help.
AF due Jan 1; TWW-ing
Here's the situation. My brother's gf told him she was pregnant last November after they had been broken up for a little while. He wasn't 100% sure it was his but he wanted a family SO bad he agreed to "make it work." Baby was born in July (early? or did she lie about the conception date?) He refuses to get a paternity test. My DH is sure she's using him and is going to stick it to him for everything he has. My mother is supportive of the whole thing and just loves this baby. (I have to admit, she's f-ing adorable)
Mother and "sil" have been encouraging us to get pregnant so that Baby can "have someone to play with."

: We don't live anywhere near them and in all honesty, don't plan on spending much time with them when we do have kids.
Rather than rushing into things or having an oops baby, DH and I have thought long and hard and have decided now is a good time to start TTC (we've been together for 4+ years, married 1) but we're afraid my family will trivialize the whole thing. No one seems to care that Baby may or may not actually be my neice and comments involving the word "playmate" just make me crazy!
So it was really hard for me being with my family for Christmas - everyone kept offering me wine, or eggnog, and although I'm still not sure I'm PG, DH and I don't want to take any chances. So my brother's nosey gf asked (loudly) "Are you pregnant or something?" and of course I said I wasn't, but that we're trying so I want to be careful. She's incredibly young and and is one of those "Pregnancy is SO fun! Babies are SO cute!" girls. :Puke
I wanted to tell my mom I'm tww-ing, but I didn't get a chance and don't feel like I should tell her yet. I have a 180-degree different idea of how children should be raised from what my "sil" is doing and I don't want any input from my self-proclaimed "Butt-insky" mother.
What do I do?