I know that on E-day, Maria sent the kids to her parents house on that day. However, when Maria's parents and kids died, they only buried her parents. In Gears 3, when Dom is asked when he was last in Mercy he says: "Maria's family, they're buried near the church. I wanted to bury her and the kids here too, but..." like what was the signifigance in that? I know he couldn't bury Maria because her body is still in the Hollow but why did he make an issue out of his kids?
P.S. I read the Sourcebook, his kids falling in an E-hole isn't canon. The entire thing goes against some events in Dom's life so we can't take that as a source.