90/180 day visa-free. Includes children ?

Does it apply to children?

Can a 4 year old be fined and banned for re-entry for 3 months the same as an adult ?

Mother has Ukranian passport. Her child only a British one with an overstay record.

Hello Michael. Children's time is not counting in Ukraine. Children till the age of 18 can stay in UA as long as they want having the relative document with a resident of Ukraine (citizen or residence permit holder).
DM me if any other questions.