In my headcannon, the two get babies; three. The firstborn has Rainbow’s mane colour. The others get different symbols.
And Rainbow proves a great mother. Instead of being concern whether each baby be boy or girlm she’s more concern if any survive…. and beats her chest and yells on joy over each baby surviving before comforting each one with her heartbeat. And she zero yells on them as Rarity, Applejack, and Twylight tend to do to kids; just a firm yet fair scolding (similar to Mufasa with Simba). And she even gets scars on her chest protecitng her kids.
And Rainbow proves a great mother. Instead of being concern whether each baby be boy or girlm she’s more concern if any survive…. and beats her chest and yells on joy over each baby surviving before comforting each one with her heartbeat. And she zero yells on them as Rarity, Applejack, and Twylight tend to do to kids; just a firm yet fair scolding (similar to Mufasa with Simba). And she even gets scars on her chest protecitng her kids.