Abigail and Rachelle Henderson, 15-year-old twins from Buffalo, New York, were conceived in vitro and carried to term by their mom, Rebecca. Trevor and Aubrey Gassman, now 9 and 8 years old, who live in Oregon, were born of embryos created during the infertility treatment of Rebecca Henderson and her husband, Chris. The couple donated the embryos through a Christian agency to Dan and Kelli Gassman, and Kelli carried them to term. Genetically, the four children are siblings. While the two families aren’t related, the parents in both families have chosen to let their kids get to know one another…