In English a "basket case" is someone who is regarded as useless and unable to cope with life. The phrase "I never knew my dad and I was a basket case" implies that BECAUSE he never knew his dad, he grew up without guidance and became a confused and screwed up person who couldn't cope with things. Wiktionary definition...."The term originated from WWI, indicating a soldier missing both his arms and legs, who needed to be literally carried around in a litter or “basket”. Today it indicates a state of helplessness, most frequently in the context of mental health or aptitude."

To me, I understand Basket case means to refer to someone as 'crazy' or 'weird' - please see this link https://www.urbandictionary.com/define.php?term=Basketcase This phrase could have two meanings depending on the context I never knew my dad and I was a basket case = Because I did not know him and therefore had a hard life I became a 'basketcase' too (ie as a result of my environment) OR My dad was a basketcase and even though I didn't know him I still became a basket case (ie it is genetic) It would all depend on the context before and after.