Two brothers c. with the same first name both living

[jim1]

With high mortality rates amongst children & the need to preserve favourite family names prompted this to happen. It's an ordinary man's version of the heir & the spare.

[watney]

Thank you so much every one who has answered my post, I think I'm going to go for "the heir and spare" theory. This couple had lost their first child at 10 months and so they might well have been afraid that the same might happen to William c. 1791 so back it up by c. William 1794.

Best wishes to you all, Brenda

[Maiden Stone]

There's that naming convention where the first born female is named after the father's mother and the second born after the mother's mother etc etc - or however it goes 

So I wonder if it could be to do with grandparents having he same name?

It's normally the other way around. 2 earlier generations of the same family as my 2 Elizabeths had 2 sons christened Richard after paternal grandfather in one case, possibly maternal GF in the other;  first Richard of each pair died in infancy.
My 2 Elizabeths were daughters no. 2 & 4. Eldest daughter had 2 names after both grandmothers; eldest son had 2 names after both grandfathers. Elizabeth may have been for an aunt.