Can a Warlock make a Celestial Pact with a Sorcerer with a Celestial Bloodline? If so, how many levels would the Sorcerer be over the Warlock who wants to make the pact?
Warlocks are seekers of the knowledge that lies hidden in the fabric of the multiverse. Through pacts made with mysterious beings of supernatural power, warlocks unlock magical effects both subtle and spectacular.
Emphasis Mine, from the Player's Handbook page on Warlocks, pg 105.
Going by just what the Player's Handbook we get a vague "Maybe, not sure, ask your DM" sort of answer. There is no real guidance in the DMG or the PHB of whether a certain creatures be a Patron.
If we look towards Xanathar's Guide to Everything, we get the following blurb from the section on Celestial Warlocks, pg 54.
Your patron is a powerful being of the Upper Planes. You have bound yourself to an ancient empyrean, solar, ki-rin, unicorn, or other entity that resides in the planes of everlasting bliss.
This is a bit more to work with. Our patron is going to be two things. 1: From the Upper Planes, or perhaps has power from there, and is 'Powerful'. It's important to note that even though it claims the creature must be powerful a unicorn is a valid patron and they only reach CR 5.
With all of this in mind? Probably not.
For starters: There is absolutely no guidance of 'A level X sorcerer can make Y warlocks and they can reach Z level' or anything of that sort, you won't find anything on that. Even without that info, the text seems to lean that your patron needs to be an actual creature from the Upper Planes and not just one that gets power from there.
But what if I want to do it anyway?
If you are the DM and want to go this route regardless of what we have in the texts, I suggest just letting a powerful celestial sorcerer (Whether you give them class levels or not is irrelevant) act as a valid patron for warlocks. Don't over complicate it with 'Oh well you can't level up because the sorcerer is only level 8' type stuff, just let it be the background of the character's patron.
I wouldn't let another player character be the warlock's patron unless you establish the warlock keeps his current powers if the sorcerer gets upset at him (There is no 'I made my Patron mad and now I have no powers' in 5e, that would all be house rules). This type of interaction is very player vs player and can lead to unsavory situations. So if you do go this route, it needs to be careful and delicate but could be a fun interaction. I'd personally let this happen as a one time thing, the sorcerer applies a blessing or does something magical to the would-be warlock and it grants them their powers. Their powers then grow on their own.