Complex sentence: Belgium passed a same-sex marriage bill in 2003, with Spain (2005), Canada (2005) and South Africa (2006) becoming the next three countries to pass such bills.
Split into simpler sentences: Belgium passed a same-sex marriage bill in 2003. Spain and Canada legalized same-sex marriage in 2005 and South Africa legalized it in 2006 thus becoming the next three countries to pass such bills.