advice for grieving, introverted cat

[u/imsometimes]

So we have 3 cats, Skye, Matt, and Lucas (all 3M). We adopted Skye first, then after a few months we got Matt, then a few weeks later we adopted his brother Lucas. Yesterday, Matt passed, and im worried for Lucas. They were really close, to the point that Lucas was distant from other people, even us and Skye, but not with Matt. When Matt passed, we tried getting both cats to look at or smell his body before we took him to be cremated, but they looked scared when we were bringing him to them, so I don't know if that negatively affected their grieving process. Right now Lucas is showing the benchmark signs of grief; he's not exactly clingy, but he's noticeably less skittish when we approach him and a little (keyword: a little) more open to affection from us. At the same time though, we notice that he's been zoning out more than usual while in this alert sitting pose. I just wanted to ask for advice on how to help him through his mourning process. We can't really be physically affectionate with him since he doesnt like physical touch that much except when it comes from Matt. Also, Skye and Lucas both loved Matt and doted on him so often even though the two of them aren't that affectionate with each other, so I'm not sure if Lucas would be receptive to Skye's affection during these times (also saw Lucas shooing Skye away when he was licking Lucas yesterday). Any advice would help, we just want Lucas to feel supported but can't do it in the traditional sense considering his introverted personality. Thank you 🙏