The twins' arrival follows heartbreak for Nikki and James last year, who lost their baby girl Elsie soon after birth.
It was a bittersweet time for the close-knit Manawatu family as youngest sister Anna - the former wife of the man police accused, and then cleared, of Scott's killing - announced her pregnancy to new partner Brent Jameson.
She gave birth to a baby girl, her fifth child, in March this year.
Midway through last month, a heavily pregnant Nikki posted a photo of her side profile on Facebook and announced the babies were weighing a bonnie 7lb 7 and 6lb 11.
Friends say the proud parents haven't stopped smiling since the girls' arrival.
Scott Guy was shot dead outside his Aorangi Rd farmhouse near Feilding in July 2010.
His brother-in-law Ewen Macdonald was charged with murder. After a trial, he was acquitted of murder but pleaded guilty to other crimes, including killing of farm animals, vandalism and arson on the family farm.
He is due to go before the Parole Board at Rolleston Prison on November 17.