you need to be more observant, gandalf referred to a family member of bilbo who he knew personally and who went on adventures and wasn't afraid of a dangerous trek, bilbo's ancestors were fallohides who were close to the elves and were different than all other hobbits, bolder and more adventurous, bilbo isn't an ordinary hobbit
And you clearly are no ordinary jackass... Gandalf never explained why he chose Bilbo. Saying that he once knew a relative of his is hardly an explanation as to why he chose to put the mark on Bilbo's door. Now go back and scour the internet and see what other irrelevant drivel yuh could find.
for people like yourself with zero intuition and foresight I will educate you further.
gandalf spoke of the family member because bilbo's lineage is indeed different than other hobbits, hinting that you are not like the rest, that is the reason why I chose you and that I know your family history. Secondly Gandalf also explains to Thorin that the hobbits scent goes undetected to orks and goblins, it is unfamiliar, it is therefore easy to sneak past enemy lines and in the the next 2 features, help them defeat smaug, by finding the invisible entrance to the once dwarve kingdom, all this was revealed in the feature.
if you want i can also add a few more points which gandalf gives to why bilbo was chosen, which was even revealed in lotr and this story, of course no ordinary but an extraordinary jackass would miss those points
