Don't we pretty much use 'to pine' in the same sense (and more senses beyond) of 'to repine'? It reminds me of the same relationship between iterate and reiterate with 're' being an intensifier, although I think here people use reiterate more than iterate, whereas they use 'pine' over 'repine.'

Some people "iterate", others "reiterate"
Either way etymologists consider them literate.
It's the same with "pine"
And it's cousin "repine"
Either way you will feel like you want to commiserate.