If you are thinking about it and asking questions, my advice is to put feeler out, look around a little and just
see what's out there. Gracie Ruth fell into my life a scant week after Annie B left. And had I not be open to at least looking I would have missed out on her AND Yogi, sense we got him from the same lady 7 months later.
When the right one comes along, you'll know it. And don't think Millie isn't watch over you and working things out so that just the one she's picked will end up with you. I know Annie had a paw in G coming to me.
And I'm all for more then 1.
I do really like the boy/girl mix the best. Just my personal experience, I'd not want them to be from the same litter. Every time Yogi and his bro Pablo get together they are at each other just like when they were littermates. Although G and Yogi play A LOT together there is something different in how littermates seem to play.
And don't worry about the bonding. Both are so bonded with DH and I. They love each other and playing together, but when Momma or Dad call they drop everything and come running.