Undecided questions
leren kennen of kennen?

Hi! It is "Hoe heb jij (mijn) mama leren kennen?" (yes you do have to put 'leren' in there, without it is not a correct dutch sentence.)
Other options "Hoe heb je mijn mama ontmoet?" (How did you meet my mother?)
"Waar ken jij mijn mama van?" (Where do you know my mama from?)
(Try using as much as you can: my, his, her, their, our ..mama (mijn, zijn, haar, hun, onze mama) - unless you're talking to your dad... then just mama is ok... he knows who you're talking about ^^)

I forgot to mention:

Another possibility: "Hoe ken je mijn moeder" (How do you know my mother) - no 'leren' needed
When you use the verb hebben (to have) then you add 'leren' = "Hoe heb je mijn moeder leren kennen."
so that should do it! :)