Curate, connect, and discover
Here's a thought I doubt anyone's ever considered before.
What if Tristan was born before the Commandments were released?
He'd be the child of a different Ellie of course, probably Liz, and Liz died shortly after giving birth to their son. As a result Meliodas showed up in Liones with two babies!
The Sins still form and all that but with the addition of Tristan being coddled by everyone because he's Meliodas' son... up until Zaratrus is killed. Meliodas doesn't have time to grab Tristan before he's teleported away so Tristan gets left behind and taken jn by Baltra. He grows up alongside his own mother as practically siblings and when Baltra is locked up and the Coup happens Trustan goes with Elizabeth to find the Sins, and also because he wants to find his father.