Blue Paladin could be Marmora, a half Altean/half Galran who was in love with Zarkon and they had a child, Lotor, during the glory days of the empire.
Marmora and Zarkon were often busy with their duties and taming the galaxy, so young Lotor grew up in the palace alongside Allura.
When the betrayal happened, Lotor was taken away and Allura left alone. Mamora was terrified and heartbroken, and took the blue lion and vanished with it, keeping it out of Zarkon's grasp, yet was unable to rescue her child.
At this point, Marmora could have founded the Blade of Marmora, and set her people up to fight against Zarkon and somehow save her son. She never was able to.
Hiding the Blue Lion from Zarkon was the last thing she was able to do, hiding away on a distant world where life was flourishing and the race of man was thriving. She entered suspended animation for a time inside her Lion, allowing herself to stay hidden and locked away...
...and then, one day, Keith's father discovered the Lion's resting place, and woke Marmora up. The pair fall in love, after a rocky road, and have a child. Marmora's fate unknown, possibly dying, possibly not.
Whatever the case, it leaves alot of possible openings... and a connection for Keith to the blue lion and allows Marmora to mean something rather poignant in the name of his and Lotor's mother.