Cheryl is from Northern Ireland - as am I!!!
Brendan is from Dublin as they aren't full brother and sister. I think they share a dad, but have different mums and grew up in different countries - Northern Ireland and Republic of Ireland are different countries.
Pete is from Northern Ireland, but has a bit of a weird accent due to the place in NI he's from. I could imagine he's quite hard for English people to understand as they accent is quite thick.
I can't believe that Silas kills Heidi! Wow! That'd be a twist and a half!