FHLBanks Split Between GSE and Non-Agency MBS The Federal Home Loan Bank System looks like its developing a taste for mortgage-backed investments, but the individual Banks are relatively split about whether GSE or non-agency securities are the way to build their portfolios. According to data gathered by Inside The GSEs from the Federal Housing Finance Board, the FHLBanks together grew their holdings of mortgage-backed securities in the first quarter by almost three times the increase