On my first Playthrough FeMU (Léna) married Yarne, because I was kinda bad at the game, and Yarne was the only eligible bachelor left alive (I had 6 Marriages in total on the run, the others being; Chrom/Sumia, Lon'qu/Panne, Libra/Tharja, Gregor/Nowi and Morgan/Cynthia.) and I actually ended up loving the supports, plus that confession scene is adorable.
Second Playthrough MaMU (Oshwa) married Cherche. I was originally intending for his wife to be Tiki (because I fell in love with her), but on Chapter 12, Oshwa and Cherche just stood next to each other (Him with Armourslayer, her with Hammer) and they tore the enemy to shreds, and so they became my duo of destuction. Plus I fell in love with Gerome/Morgan as siblings, and Pink haired Morgan is adorable. (Also my Morgan/Oshwa combo against Grima felt good for me. GriffonRider!Morgan flies Hero!Oshwa up (2 turns to reach Grima), And kills on first battle with Brave Sword (3 Strikes))
Third Playthrough FeMU (Gaia) married Chrom, mainly because I wanted to see what Frederick!Cynthia was like, but I also wanted to see how it affected the storyline of the game too. Whilst I enjoyed it, not my favourite pairing for either Character, but not my least favourite either.
Fourth (Current) Playthrough MaMU (Robin) will marry Tiki. This is my favourite pairings file, based upon supports/personalities. I haven't recruited Tiki yet, but I'm close (1 Chapter away from unlocking her Paralogue), but I have all my other First Gen Parents married, and soon hopefully the children too. My reasons for picking Tiki, is that I love her support with the Avatar, and she's my Fav Female Fire Emblem Character.