Dominic finally got the hang of it somewhere between 3 and 4 months. Natalie was earlier. With Natalie, I got her using the pacifier as well.. Dominic is a no go with the pacifier!!
DD sucks her thumb and takes a pacifier. She didn't consistently hold the pacifier in her mouth until closer to 3 months. The thumb was off and on the whole time. Now, DD prefers sucking on her fingers.
M has been teething for about 2 weeks now and she found her thumb then. She doesn't really suck on it though more like chews on it. She does take a paci but would rather chew on her thumb.
Liam found his around 3 months, but just for something to do I think, not to self soothe. He sucks his thumb often now, but he's still not self soothing with it.
Re: moms of thumb suckers...