I was told today there is a child in my 2 yrs old daycare group whose brother has chicken pox. how likely it is for my toddler to get chicken pox?

Depends: In the US kids are usually vaccinated against Cpx at 1 and 4-5.If your kid received the vaccine, s/he is likely immune.If not, and not in contact with a case, no problem.However,if the brother your kid plays with gets cpx, he is contageous from a day before the spots appear.It is very contageous and easily transferred from active cases, but not through a third party.