Yūkimaru’s favourite flowers are white camellias. Because of his connection to the Three-Tails, Yūkimaru is also believed to have some connection with its former jinchūriki, Yagura. The two also have similar appearances, and both have an apparent connection to flowers, however, Yūkimaru is an anime-only character.
Yūkimaru encased in crystal as Guren prepares to fight. Later, Kabuto conducted another experiment with Yūkimaru, by consuming more pills than the first time, he was able to completely summon the Three-Tails. The strain caused his nose and ears to bleed, and he soon passed out, causing the beast to go on a rampage.
So if I really had to guess, based mostly on the flashback (where Guren is at most 14 and Yukimaru has to be at least 4) there are ten years between them and when we see them in Naruto Shippuden, she is 21 and he is 11.