Katharine Hill, UK director of Care for the Family, told Premier's News Hour: "I think you've got a kind of ready-made community there - there are older siblings that can show younger siblings, lead the way for them, at meal times you've got sort of readymade conversation."
She was commenting after new research by Eurostat showed that four child families are now far more common, and Britain is trending towards birthing levels seen in the 1970's.
Part of this has been put down to immigration, but also to wealthy parents having more children than before.
Katharine Hill continued: "It is as expensive to heat a house for four children as it is for one, you'll probably use more hot water and the food bills will be more expensive, but you can share things, you can hand things down - so it's not four times more expensive to have four as it is to have one."
Figures from Eurostat show that in 2013 9.5 per cent of babies born in the UK had three or old more older siblings and across Europe four children families are more common in Roman Catholic countries.
Listen to Premier's Hannah Tooley speak to Katharine Hill here:
