When my ex husband renews my childs passport will my passport number be required?

My daughters (aged 15) passport has expired and because my ex husband, her father, is taking her on holiday soon he has said he will sort out her passport. He has asked me for my passport number and I am not entirely sure why - does he need this? I cannot remember needing his when I renewed it previously. I am a bit dubious as we are not on the best of terms and it has only asked for it via a message through my daughter. Thanks any ideal would be appreciated