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Levi Johnston is going to be a dad again.

A source close to Bristol Palin's ex-fiance told ABCNews.com that Johnston's girlfriend, Sunny Oglesby, has been pregnant for "about four or five months." The source would not comment on whether the two plan to get married.

Johnston, 21, and Oglesby, 20, have been dating for a year.

This will be the second child for Johnston, who fathered a son with Bristol Palin, the eldest daughter of former Alaska governor Sarah Palin, in 2008. Johnston and Bristol Palin called off their engagement in March 2009, got engaged again in July 2010, and split up once and for all weeks later.

Johnston's 2011 book, "Deer in the Headlights: My Life in Sarah Palin's Crosshairs," claimed that Bristol Palin wanted to get pregnant because she was jealous of her mother's pregnancy with son Trig. Having a baby of her own, he wrote, was exactly "what she wanted."