Hypothetical question

[Margaret in Burton]

This is niece's hubby's tree again

Can't name names as at least 3 of these people are still alive.

I have a marriage in 1923 in Godstone, Surrey. He was in the Grenadier Guards so perhaps why they move around so much.

Not common names and the only one on the whole of Ancestry or FreeBMD with that combination of surnames marrying.

I have found five children.

1: Dec qtr 1923, Mere, Wiltshire

2: Dec qtr 1930, Chelsea, London

3: Mar qtr 1931, Dorchester, Wiltshire

4: Jun qtr 1937, Derby

5: Jun qtr 1947, Burton

All the same mothers maiden name.

2, 4 and 5 certain same family as they are known about in the family

Number 1 is as well as there is a christening on Ancestry that confirms the parents (dad has a very unusual first name, the same as child number 2- the only ones listed from 1837-2005)

Child number 3 is my problem. I know it's the next quarter to number 2 but a different district. I know we could get the birth cert but this family is proving so complicated that it's going to cost a fortune anyway by the look of it, so trying to economise where possible.

My question is: Could they have been twins but only one was registered in Chelsea and the other in Dorchester in the next quarter?

I have found child number 1 still alive. He may know the answers. I have an address and a phone number, but as the rest of the family don't appear to know he exists he may want to meet his 2 sisters still alive. They believe that their mother was someone else and it's a bit late in the day to tell them different.