Should I pursue a friendship with the younger sister instead?

the older sister would be a couple years older , i meet them both at there work , they both worked at same place during the summers. the older sister is in the city doing other stuff rate now and haven't seen her for about a month. during the summer was really interested in being friends with her but don't think about her much now. the younger sister still works there but not during the winter so not sure i will see much of her either although been talking to her last few times i was there , we seem to get along well , she has a boyfriend but he's out of the country for about a year and not sure what she's doing to keep busy

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i don't actually follow either of them on social media but though about adding the younger one recently but her page is set to private , also think she might be done that job for the season so not sure if i'll see her around much now , she was very comfortable talking to me at work but not sure how it would go online
Should I pursue a friendship with the younger sister instead?
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