I prefer not to use Ewan because you get him later in the game and he's so hard to train haha. I turn Cormag into a Wyvern Lord and Tana into a Wyvern Knight so I pair them up too anyways haha. As for Olivia+Chrom, it's easy! Just keep Chrom away from other girls and then in the episode were Olivia jumps in, just have her dance to him like 20 times lol. Rightful King Inigo is quality.
well i've done it once already but its really demanding on higher difficulties since sometimes you wont get to choose who you pair up with. i think i did it by marrying off every single wife candidates of Chrom and having Olivia and Chrom pair up on that chapter. also how can i even dance 20 times on that chapter? Gangrel moves on Turn 5 or something near that and every single enemy on the map is aggroed against you so you cant stall for time either. i think Rightful King would be great with Lethality but since no child bar Morgan can have that skillset its not really viable. ugh if only Lissa and Chrom weren't siblings and could marry >.<