There are quite a few threads on here about getting a second Cocker and most of the answers on them are positive and the new puppy and existing dog have bonded, sometimes immediately, sometimes after a few days, weeks or even months. But it doesn't always work perfectly.
I have William and Louis. William was 5 years old when Louis came home. William's a very confident dog and his body language around other dogs is very good. He's non confrontational and gives lots of calming signals. He prefers human company to other dogs so I didn't expect him to fall head over heels in love with Louis but I didn't expect him to be completely horrified and become withdrawn. But that's what happened and while Louis was young and needy (exceptionally needy in his case) poor William spent most of his time on his own, taking himself off upstairs or in a different room, anything to be away from Louis.
I made special time for William of course, but it pretty much broke my heart at the time and didn't get me and Louis off to a good start in our relationship because I felt resentful at times, as well as being exhausted from having such a needy puppy to look after.
3 years later and the boys tolerate each other and seem to live companionably without causing each other too much stress. There's the occasional brief outburst of jealousy, usually if I'm sat on the floor playing with one and the other approaches. Then there will be growling and maybe a 2 second scuffle. I just get up and walk away and ignore the behaviour, no point in shouting or doing anything that might escalate it.
I can honestly say that they have never played together and never share a bed. Louis would love to play or snuggle up but William just walks away. I think he's still hoping that Louis is just a visitor and will leave soon

As Ruby Tuesday has said, when you get a second puppy you need to make time to walk and train it on it's own some of the time. That helps you to build up a bond with the puppy and it won't become overly dependant on your older dog. I hoped that Louis would learn some good behaviours from William but it's turned out the other way and William has picked up on a few of Louis's anxieties

I'm not trying to put you off at all, just to make you aware that sometimes, despite all the hard work, you end up with a less than perfect situation. I'm just very grateful that mine have learned to tolerate each other well enough that I feel they're OK living together and it's not causing them endless stress.