This is all a bit crazy but basically Leia discovers/knows Luke is her twin. She believes they're meant to rule together and 'be' together for everything (but not actual incest). So she installs a naive young Luke as prince/consort/whatever, and then when Han comes into their lives, there is no question for her that he will court them both, since he's clearly so taken with her and Luke.
Han eventually marries both Luke and Leia, and they all raise their children together.
Don't mind how events unfold.
Bonus: 1. An A/B/O universe where Luke is omega and so Han sires children with both him and Leia. The children are both siblings and cousins and are dreadfully confused, but figure at least they're not actually inbred. 2. Han is Alpha but the roles are not necessarily defined and so he answers to Leia a lot, or she's Alpha too. 3. Vader arrives to the scene late and is just as confused as his grandchildren as to what's going on. 4. Possible dark!Leia has plans to rule over the galaxy with her husband and brother, and so maybe she and Vader get along all right, all things considering.
Han/Leia/Luke, (not incest), Leia & Luke rule together, possible mpreg and a/b/o verse
Han eventually marries both Luke and Leia, and they all raise their children together.
Don't mind how events unfold.
Bonus:
1. An A/B/O universe where Luke is omega and so Han sires children with both him and Leia. The children are both siblings and cousins and are dreadfully confused, but figure at least they're not actually inbred.
2. Han is Alpha but the roles are not necessarily defined and so he answers to Leia a lot, or she's Alpha too.
3. Vader arrives to the scene late and is just as confused as his grandchildren as to what's going on.
4. Possible dark!Leia has plans to rule over the galaxy with her husband and brother, and so maybe she and Vader get along all right, all things considering.