Legally removing a middle name on birth certificate for a baby under 1.

Unsure how to, if at all possible to go about this one!

When choosing our baby’s name we chose to honour my partners dad in baby’s middle name choice (he had two middle names his was one of them) baby is currently 7 months old and this person we chose to honour makes ZERO effort to be in baby’s life. He hasn’t seen him since he was a month old and makes no effort at all and to be honest we’re exceptionally disappointed.

We have decided to remove said family member in our baby’s legal name but would like to know how to go about this and can it be changed on his birth cert?

Thank you in advance.

Please note this isn’t a spiteful removal, this is because the person involved (grandparent) we don’t want any awkwardness down the line in the future when we have to explain bays name choices to him and explain we chose to honour someone who doesn’t make any effort to see him!