One maintains such a low profile that even his nationality is hard to pin down – born in Estonia, educated in Israel, and minted through penny stock trades in the US. The other is a Kildare-based builder who went bankrupt a decade ago with debts exceeding €100 million and was later accused by the British insolvency authorities of attempting to “cheat creditors”. But the one thing that unites David Grin and Paddy Byrne is Victoria Homes, a high-end housebuilder that has snapped up a string of sites in well-heeled suburbs of Dublin. Byrne, as of late last year, owns 100…