A study in Australia indicates siblings are healthy. Specifically, if you had brothers and sisters when you were young, you could have a lower risk of developing multiple sclerosis.
The report in the Journal of the American Medical Association indicates exposure to infants before a child is six years old may boost the immune system and lower the risk of some autoimmune diseases like MS.
In the study, led by researchers at Menzies Research Institute in Hobart, Australia, researchers found increasing the duration of contact with younger sibling less than 2 years old in the first 6 years of life reduced the risk of multiple sclerosis. 1 to 3 yeas of infant contact reduced the risk to 43%, 3 to 5 years of contact a 60% lower risk and more than 5 years of infant contact an 88% lower risk