Most 20 year old 'men' have the mentality of a 13 year old boy.
My daughter was seeing a 19 year old lad when she was 15, I realised I couldn't stop it without causing major upset to everyone concerned, so I talked to them both about it and made sure my daughter was on the pill. They spent most of their time at my house just watching TV and listening to music anyway. They went on to have 2 children together when my daughter was older, unfortunately they split and my daughter (22 years old now) is bringing up the children on her own.