You have my deepest heartfelt sympathies, understanding and happiness. I hope I can convey what is in my heart. I see something in Oliver that I see in my boo and that is affirmed through your writings of him. Tikkanen's signature reads "Until one has loved an animal, a part of one's soul remains unawakened". I truly believe this, as my Pax has done this for me, awakened something at my very core, and it seems that Oliver has done this for you also. Others here have mentioned how their connection is that of a soul mate or as Jon730 refers to, "a Cat Wife" (which to me is the same as soul mate). I believe this for you and Oliver as I too share this connection with my beloved Pax. It is as if he has crawled into your earth suit with you and the awakening is oneness. For me this has been on a level I have never experienced with any other living creature. It was/is truly spectacular. This is something you do not get over and you're not supposed to, it's a gift.
When our significant other has to leave us it is devastating but we do get through, although it be quite a bumpy ride

Pax grew up with his half sister (Tatia) but they were never close. They were much like two people who have nothing in common. My vet said he bonded to me and my girl bonded to food

On the eve of Pax's transition I like you did not want to be in my apartment. I really wanted nothing to do with my other "cat". The next day I realized that it was not fair to take love away from Tatia just because Pax was not around. I proceeded to tell her, as I have done before and as I had done with Pax, how much I love her because if it's one thing Pax taught me it's love.
Tatia is not Pax and never will be, no one will be because Pax is Pax, as Oliver is...well, Oliver. That can not be erased, changed or ignored because of our merging with their souls. But Tatia is special and she is trying to help me heal much like your kids are trying to help you heal. Let the love that Oliver has awakened in you be, as it will not change Oliver nor your connection to him. I can not stress any of this enough.
You, Sarah are a very dear soul and I feel as if I know you, and Oliver, well, when I say his name it makes me smile. I am so happy for you that you were able to partake in Oliver's journey and receive the gifts that he has bestowed upon you. I often use the term magical when referring to my bond with Pax and yeah, I feel that for you and Oliver.

One way that I have found to honor my bond with my boo is a locket. I found a place (picturesongold), online that has 14K gold lockets with a paw print etched on the front (see above picture). The paw etching looks much better in person. You send them a photo and they laser etch the image (color or black & white), on the inside of the locket. The etching is "exactly" as your photo and is water resistant (I never take mine off). The image I have of Pax is my avatar, it was a picture taken a half hour before his transition. I also found a place that sells very attractive cremation jewelry (keepsake jewelry), since you have Oliver's ashes that you may be interested in.
Keep your heart open it is what Oliver has helped you to do. I believe we will see our loved ones again, and depending on what you believe you may see them again in this lifetime. I wish much love and peace on the rest of journey.
cheryl, pax & tatia