So far, I have 50 MUs in my Avatar Logbook. And with so many pairings, I don't know how many there are. So I decided to count how many pairings there are as well as how "popular" the pairing be... I have to say, there are some pairings that surprised me of how "popular" they are. Anyway, I thought I might share my counts to you and let you guys think about the list:
Number of MUs = 50
MU/Inigo = 1
Gregor/Cherche = 2
Chrom/Olivia = 2
Lon'qu/Cordelia = 2
Gaius/Sully = 1
Virion/Panne = 1
Kellam/Miriel = 2
Libra/Lissa = 1
Henry/Maribelle = 2
Frederick/Sumia = 3
Ricken/Tharja = 1
Donnel/Nowi = 3
Kellam/Olivia = 2
Ricken/Maribelle = 6
Vaike/Panne = 3
MU/Miriel = 2
Gaius/Cordelia = 3
Chrom/Sumia = 16
Donnel/Lissa = 2
Lon'qu/Tharja = 2
Gregor/Nowi = 3
Virion/Sully = 11
MU/Tharja = 3
Kellam/Cherche = 2
Frederick/Cordelia = 3
Stahl/Sully = 7
Vaike/Lissa = 6
Lon'qu/Panne = 6
Virion/Miriel = 2
MU/Olivia = 1
Vaike/Miriel = 2
Stahl/Cherche = 3
Inigo/Noire = 1
Henry/Tharja = 2
Gauis/Nowi = 1
Lon'qu/Maribelle = 1
Ricken/Lissa = 2
Gregor/Miriel = 1
Vaike/Nowi = 2
Kellam/Panne = 1
Donnel/Sully = 1
Stahl/Olivia = 1
Stahl/Cordelia = 4
Frederick/Cherche = 1
Henry/Olivia = 2
Frederick/Panne = 3
MU/Chrom = 5
Gauis/Sumia = 3
Henry/Lissa = 1
Owain/Noire = 1
Laurent/Cynthia = 1
Gerome/Lucina = 2
Brady/Severa = 1
Ricken/Nowi = 2
Donnel/Maribelle = 1
Owain/Kjelle = 1
Frederick/Lissa = 4
Henry/Miriel = 1
Gregor/Panne = 2
Lon'qu/Cherche = 1
Frederick/Sully = 1
MU/Panne = 2
Chrom/Sully = 1
Donnel/Cordelia = 3
Gregor/Olivia = 1
Virion/Cherche = 2
Lon'qu/Nowi = 1
Ricken/Miriel = 8
Owain/Severa = 1
MU/Lucina = 1
Lon'qu/Lissa = 2
Virion/Olivia = 1
Stahl/Tharja = 1
Gaius/Lissa = 1
Henry/Nowi = 2
MU/Lissa = 1
Lon'qu/Olivia = 2
Chrom/Maribelle = 1
Libra/Olivia = 1
Libra/Tharja = 3
Libra/Cherche = 1
Libra/Nowi = 2
Libra/Cordelia = 1
MU/Cordelia = 2
MU/Anna = 1
Kellam/Sully = 2
Chrom/Maiden = 1
MU/Sumia = 1
Kellam/Lissa = 1
MU/Inigo = 1
Gregor/Cherche = 2
Chrom/Olivia = 2
Lon'qu/Cordelia = 2
Gaius/Sully = 1
Virion/Panne = 1
Kellam/Miriel = 2
Libra/Lissa = 1
Henry/Maribelle = 2
Frederick/Sumia = 3
Ricken/Tharja = 1
Donnel/Nowi = 3
Kellam/Olivia = 2
Ricken/Maribelle = 6
Vaike/Panne = 3
MU/Miriel = 2
Gaius/Cordelia = 3
Chrom/Sumia = 16
Donnel/Lissa = 2
Lon'qu/Tharja = 2
Gregor/Nowi = 3
Virion/Sully = 11
MU/Tharja = 3
Kellam/Cherche = 2
Frederick/Cordelia = 3
Stahl/Sully = 7
Vaike/Lissa = 6
Lon'qu/Panne = 6
Virion/Miriel = 2
MU/Olivia = 1
Vaike/Miriel = 2
Stahl/Cherche = 3
Inigo/Noire = 1
Henry/Tharja = 2
Gauis/Nowi = 1
Lon'qu/Maribelle = 1
Ricken/Lissa = 2
Gregor/Miriel = 1
Vaike/Nowi = 2
Kellam/Panne = 1
Donnel/Sully = 1
Stahl/Olivia = 1
Stahl/Cordelia = 4
Frederick/Cherche = 1
Henry/Olivia = 2
Frederick/Panne = 3
MU/Chrom = 5
Gauis/Sumia = 3
Henry/Lissa = 1
Owain/Noire = 1
Laurent/Cynthia = 1
Gerome/Lucina = 2
Brady/Severa = 1
Ricken/Nowi = 2
Donnel/Maribelle = 1
Owain/Kjelle = 1
Frederick/Lissa = 4
Henry/Miriel = 1
Gregor/Panne = 2
Lon'qu/Cherche = 1
Frederick/Sully = 1
MU/Panne = 2
Chrom/Sully = 1
Donnel/Cordelia = 3
Gregor/Olivia = 1
Virion/Cherche = 2
Lon'qu/Nowi = 1
Ricken/Miriel = 8
Owain/Severa = 1
MU/Lucina = 1
Lon'qu/Lissa = 2
Virion/Olivia = 1
Stahl/Tharja = 1
Gaius/Lissa = 1
Henry/Nowi = 2
MU/Lissa = 1
Lon'qu/Olivia = 2
Chrom/Maribelle = 1
Libra/Olivia = 1
Libra/Tharja = 3
Libra/Cherche = 1
Libra/Nowi = 2
Libra/Cordelia = 1
MU/Cordelia = 2
MU/Anna = 1
Kellam/Sully = 2
Chrom/Maiden = 1
MU/Sumia = 1
Kellam/Lissa = 1
In case you're wondering why Libra is more organized than others, it's because I've made an error when checking the list and had to recount on Libra pairings. sweatdrop