My best thought is to set up a shrine in a shut away, private, and quiet place with your Oscar and Nenu's ashes, and/or pictures, pictures of spiritual things close to you. Keep fresh flowers always there. Go there to let out emotions, pray, meditate, etc. When not there and your passed babies come to mind- just try to have feelings of the love, affection, playing, petting you had for them.
It could be inevitable that some reminders of your passed ones will come up with the new babies. Sometimes you might see Oscar and Nenu instead of the new ones who are actually physically there. Just don't think too much of that, think of love, and let this pass.
May what you believe as a higher power, peace, love, happiness be with you in your grief for those passed sweet hearts. One day they could very well be with you again by a Rainbow bridge and could be rainbows in the skies too!! Love, peace Fi.