"SONG OF MYSELF" by Walt Whitman
"The young sister holds out the skein while the elder sister winds it off in a ball, and stops now and then for the knots"; This seem's to be pointing out the unity of family and siblings. For the most part familys usually get along well. In some cases though they argue (knots) but then they get over it and now matter what familly is familly.

"The young fellow drives the express wagon (I love him yet I dont even know him)". This could be multiple things; Whitman might be saying he likes the express wagon driver for all the good he does for the community and low pay. Another case would be Whitman may be gay and fantizize about this person and is afraid to admit the truth. There is no clear way of translating this.