Is it redundant to use "lake" and "la baba" together?

Why is lake included?

It IS redundant an unnecessary

But....It isn't enough to say - jina la baba ni Juma ?

They are BOTH correct - "His name, the name of his father, is Juma." - However, yes, it is unnecessary and "Jina la baba ni Juma." would be more commonly used. (that is if you have mentioned the father before; otherwise the "lake" emphasizes that it is the father of the person you are just speaking about.)