The children could share if they had too. I have a 3 bed with me oh and 3 kids.. The 2 younger ones share the larger bedroom and eldest in own box room. You make it work for you. If you had a girl they could share for several years without problem, storage is an issue but hey you get by.
Unfortunately this is the problem with taking the massive step to owning your own property you can't just ask for a bigger one.
My sister is in a council property and has been for 12 yrs. Eldest daughter 13 boy of 11 sharing their room!! Now has 4 month old baby too but is so low on councils priority list. It's disgraceful but what can she do