Naomi Osaka called Serena Williams her 'mom' on Twitter, and the Japanese star received a mix response to her comment.The 22-year-old shared a picture of her and Williams at the Rod Laver Arena on Wednesday during a charity match, alongside the caption: "Me and my mom lol.""I love this. 2 beautiful, strong women supportive of each other" read one reply, while another, from the US Open, said: "We [heart emoji] this."However, others criticized Osaka for labeling Serena as "old", with some even calling the post "disrespectful."Visit Business Insider's homepage for more stories.Naomi Osaka called Serena Williams her 'mom' on Twitter on Wednesday.However, the likely kind-hearted gesture from the Japanese star has received mixed reactions from fans and fellow athletes."Me and my mom lol", Osaka posted, alongside a picture of her and Williams sat courtside at the Rod Laver Arena during a charity match to raise funds for the Australian bushfire appeal.me and my mom lol. pic.twitter.com/HvCoPpgShm' NaomiOsaka''''' (@naomiosaka) January 15, 2020The post was met mostly with a positive reaction."I love this. 2 beautiful, strong women supportive of each other", said one reply, while another read: "Two great players. Now do like your mum. Go out there and dominate the circuit."The US Open's official account said: "We [heart emoji] this", and Women's NBA star Monique Curry reciprocated the gesture, replying a heart emoji of her own.we '' this' US Open Tennis (@usopen) January 15, 2020However, not everyone was as keen on Osaka calling Williams her "mom.""I think this is disrespectful to Serena," read one comment. "Yes Serena is much older than Naomi but girl have some class and respect! Serena is a legend and I think your comment is passive aggressive and mean spirited. Serena is NOT your mom she is your competition."Another read: "You saying Serena is old!", while somebody else suggested Osaka posted the picture because she "felt bad" for beating Williams in last year's US Open final, while also calling Williams a "complainer."So intense was the backlash, Osaka was forced to respond."I literally would not be here without her," the 22-year-old said on Instagram, where she also shared the photo. "If that's not some definition of mom idk what is. But sure, get offended by my internet slang I guess."The charity match in which both stars were partaking when the snap was taken raised $3.5 million in total, all of which will go towards helping repair the devastation caused by the fires across the country.At least 28 people and half a billion animals have died across Australia since July 1, while an estimated 14 million acres of land have also been scorched.Third seed Osaka faces Marie Bouzkova in the first round of The Open on January 20, while Williams, whose seeded eighth, takes on Anastasia Potapova.Read more:A Canadian tennis player called Rafael Nadal and Roger Federer 'a little bit selfish' for not speaking out about the poor air quality at the Australian OpenThe tennis player who collapsed at the Australian Open because of smoke from nearby bushfires says players are 'pissed' at the organizers for not taking 'better care' of themNick Kyrgios will donate $200 for every ace he serves this summer to the victims of Australia's bushfire crisis15-year-old Coco Gauff joked about going out for a drink when she was being left out of the action in a 'Rally For Relief' doubles game ' 'but I'm too young'Join the conversation about this storyNOW WATCH: 5 things about the NFL that football fans may not know Click here to read full news..