At 14 months, you would have to consider that your dog is starting to think that he may be due for a promotion in the pack. You didn't say if your sister lives with you and the dog. A quick and dirty way to overcome the humping could be for her to take over the feeding duties. This sends a powerful message. If you have any control over the dog, you should be around to supervise this. She should have the dogs food in one hand and be eating some human food with her other hand. When, and only when she finishes eating she should put the food down for the dog. Making puppy sit before she puts the food down will add to the effect. I would make this a permanent regime.
Other tricks that keep a dog respectful; before you pat the dog, make it obey a command. Always insist on going thru a door before the dog. If the dog beats you, call it back and go thru before the dog. When you walk the dog, insist on a slack lead. As soon as the lead goes tight, make the dog sit and look at you. Every time until he always does it your way. Never allow your dog to jump up on you. when he tries lift your knee up in his way so he can't reach you. If your dog is trying to demand your attention, cross your arms and hold them out from your chest, so he is unable to make eye contact with you. Get a dog matress if your dog is allowed indoors and never let him on the human furniture. I've even heard it said that when you are around your dog, hold your head high and stick your chest out like you are the most important thing in the world. I can't vouch for the last one.
If a dog is used to getting his own way all the time, he will think that there is no real leadership in his pack. He probably wont want to take on the responsibiliy, but he will feel that he has to for the good of the pack. You need to make everyone in your household aware that the dog gets nothing on demand. If he wants anything, a pat, food or even a look, he has to do what he is told first. Every dog needs to know sit, lie down, heel and come. You need to demand one of these before the dog gets anything that it might want. Its important that everyone is on board for this coz if one person doesn't do it the dog will see them as a pushover that can be dominated if he needs to do that.