Lyonel Baratheon's kids? [spoilers main]

The show has clearly aged up Lyonel quite a bit which makes it pretty difficult to believe he would be bethrothing his own child to Egg's first kid (who won't be born for another 10-15 years). We also know from Baelor's conversation with Dunk that Lord Baratheon (assumed to be Lyonel's father) held a tourney to celebrate the birth of a grandson "many years ago" in which he unseated Ser Arlan and was before Dunk was Ser Arlan's squire (he wasn't there, he just heard about it). So this supposed Baratheon grandchild is already at least a teenager based on the timeline of events.

I mean MAYBE Lyonel has a random surprise later in life baby but now it seems more likely to be his granddaughter that Duncan spurns to marry Jenny. It's also now confusing who exactly Ormund is in relation to Lyonel lol