No, a bishop does not need to be married or have children. The Lord Jesus is described as a ‘bishop’ (an ‘overseer’) in 1Peter 2:25:
For you were straying like sheep, but have now returned to the Shepherd and Overseer [bishop] of your souls.
However, the Lord Jesus never married or had children; so, a bishop does not need to be married or have children.
The requirements in 1Tim. 3 (and Titus 1:6) are written in such a way as to insist that a bishop who is married must be the husband of only one wife,1 and that a bishop who does have children must be a father who his children respect and obey. If someone is not married or does not have children (like the Lord Jesus wasn’t married and didn’t have children), then these elements do not apply to them if they desire to be a bishop.
1. See What does “wife of one husband” mean in 1Tim.5:9?