Ianto is very much a part of our family. If someone asks me how many children I have, I never hesitate to answer "two", though the rest of my answer differs from person to person. Sometimes I'll add that Amelia is the only one who gets to live with us, or that her brother died before birth. Other times I'll leave it unless someone asks why I've only got one hanging around me. He's included on a lot of birthday cards we send, and the few times we've had to put notices in the newspaper he's been there with "(dec.)" after his name.
He influences a lot of what I do. From his and Amelia's birthdays being part of my phone unlocking passcode, to having a lot of rainbow items around the house, he's there. Some days Amelia and I wave good morning or goodnight to his photos. She's been starting to point at his cabinet lately, though that may be that she wants to play with the teddy bears and other toys.
I've mentioned that I don't believe in a higher power, that I'm not sure there's an afterlife at all, but the memory of him is always around. He is represented in family photos by his teddy bear, his name embroidered on the front. Rainbows surround us, the symbol we've chosen for him. We love him just as much as Amelia.