The newly engaged couple hope to have a baby on the way when they walk down the aisle later this year, reported Ace Showbiz.
"Sofia and Joe will use a surrogate, but the baby will be their biological child, conceived with Sofia's egg and Joe's sperm," a source said.
According to the insider, the pair have been "screening potential surrogates since December, as they are excited to expand their little family."
"It's a closely guarded secret why Sofia won't be carrying the baby and not something they're openly talking about. One thing is for sure, though: They can't wait to be parents!" the source added.