And two months after splitting from the Hollywood superstar, Nina Agdal is said to be moving on with another eligible bachelor, Jack Brinkley-Cook, A source told New York Post's Page Six that things are 'serious' between the Sports Ilustrated model, 25, and Jack, 22, who is the son of Christie Brinkley and Peter Cook. The insider continued: 'They are really cute together,' following reports the new couple were kissing in public while in Montauk, New York. Despite their very public display of affection, another insider insists that they are merely having fun as part of the Fourth of July celebrations. A Instagram snap taken from the weekend showed Nina and Jack enjoying the festivities with friends - among them Jack's sister Sailor - who was ringing in her 19th birthday with their friends at The Surf Lodge. MailOnline have contacted Nina and Jack's representatives for comment. This appears to be Nina's first relationship since her low-key romance with Leonardo, 42, who she was first linked to in May 2016. In May 2017 it was confirmed they had split, with a source telling DailyMail.com: 'They both decided it was a good idea to break up. 'They are staying friends and are on good terms.' Pucker up: Nina was reportedly spotted smooching her new man over the 4th of July weekend as she enjoyed a holiday in Montauk, New York, with friends In July, Nina's grandmother Lona confirmed the couple's romance, and jokingly warned the actor to 'behave' around her granddaughter or else he would have to answer to her. She told MailOnline: 'We have not said hello to him but we hope that he behaves towards her. Otherwise he will get me to deal with. 'I can tell you that it is six years since they first met, and now the relationship apparently developed.'