I moved here with my then 13yr old son to live with my USC husband and his 2 kids. We started seeing each other, long distance, in 2011. Before we got married in 2014 we had introduced the kids to each other, spent vacations together, planned the future with them, it wasn't until 2016 were we able to move here and live together. I certainly wouldn't have moved here let alone got married unless I knew the kids, all 3 of them, were well acquainted and I knew the parenting style of my hubby.
In this journey we all take leaps of faith of varying degrees, your level comfort with this risk is yours not ours.
Good Luck.