iMessage group returning individual messages

Hi. Looking form some help. I kept getting some messages tonight which made no sense from family. It turned out my brother in law had started an iMessage group message to sort out Xmas day. All users are on iPhone and rather than being included in the group and seeing the group I was getting their individual replies to the group as seperate messages from them as individuals. Some in the group got normal messages as a group, some didn't like me its all very random.

Anybody know what the problem is or how we can fix it. We went to whats app in the end as since iOS 7 iMessage is being very unreliable.

Sorry should have said I'm using iPhone 5S and all the others are on 5 or 5S mixture of Vodafone UK, Orange and 3 Networks