Only one. No matter what part of the franchise 你 look into, they have only one child.
The cub at the end of the first film and Kiara from the sequel film are one and same character as confirmed 由 the film's creators, and that in the first film it was simply called "Fluffy". Hence, watch the video below.
In the 图书 they also have only one child. In a series of 图书 it's a son named Kopa. In other 图书 it's an unidentified son, (because those books' stories contradict the series wherein Kopa is, making it impossible to be Kopa in those books, too). In yet other 图书 it's a genderless cub because the books' ending doesn't mention a gender. And, in some 图书 it's a daughter because the ending mentions it's a female.
Simba and Nala have 3 kids acordding to the legends they have an older son named Kopa who was attack 由 Zira and never went back to Pride Rock and then in the 电影院 they had Kira there only daughter and now thanks to The Lion Guard there last kid is Kion. So there 你 have it Simba and Nala actually have 3 kids.
In the movie universe they have only one child. The cub at the end of the 1st movie is the same with Kiara (or a different version of her cuz i know they don't look alike and the ceremony looks different as well). In the 图书 they have still one child, Kopa, which does not exist in the movie universe.
They have only one which is Kiara but soon will be two since Kion is 说 to be born and would of been three cub if Kopa (the first cub and son of Simba and Nala in the 图书 which never made it to the movies) was part of the 秒 movie 或者 was even shown to be born. :^/
i think Simba and Nala have two cubs. First of all, at the end of the first movie, Rafiki is holding up a cub, and in the 秒 movie Nala is bringing a cub to Rafiki. So i think they have two cubs, no one.
In the movie universe they have 2. The first cub matched Kiara's original design. Since the first cub was labeled as " Fluffy" they must have not thought of a sequel yet. Also It never says in the movie how long Simba & Nala lived in the Jungle. So Zira possibly is a little younger then Scar but a little older then Nala. Let's say Zira entered the Pride during Scar ' s Reign at the same time Nala left. She then became mates with Scar while Nala was mates with Simba in the jungle. Then Nuka was born to Zira and scar. 3 years later Vitani is born. 1 年 later Kovu. In the last 年 with Nuka 5. Vitani 2 and Kovu 1 Simba takes over. Nuka looks 17 in Lion king 2 simba's pride. And Vitani looks at least 14/13 count lack of size due to lack of 食物 and drink. while Kovu 13/12. So 由 the time Kiara was 4. Vitani would be 14 with a . Kovu 12. Vitani looks the same size as Kovu due to lack of 食物 and water in the Outlands. Kion was an infant when Kiara was shown as a cub in lion king 2 simba's pride. Which would explain Nala's small role during the beginning. Years later Kiara seems to be 11/10 meaning Kion still having spots whom is 3 years younger than Kiara would be around 7/8 enough to possibly still have spots and start out a hair tuft. In the book universe they have 1 Kopa. Who's rich yellow color would match Simba and Nala's color mixed. But he isn't canon as confirmed 由 Disney. Fluffy is Kiara. Not Kopa. So my answer is if your talking about the book universe. 1 Kopa. If your talking about the movie universe. 2 Kiara and Kion. If your talking about the book universe+the movie universe 3. Kopa, Kiara, and Kion. If your just talking about Canon 2 Kiara and Kion.
They have 2 cubs. Kiara was their firstborn and heir to the Pridelands. Kion is their 秒 cub and leader of the lion guard. Kopa is fanmade and not canon because he simply doesn't exist in the movie universe.