10. Mourning if the deceased asked not to be mourned:[1] 

If the deceased requested not to be mourned, he is not to be listened to, and all relatives must guard the laws of Shiva and Shloshim as usual.[2] [If, however, the deceased requested from his children not to keep the 12 months of mourning, then it is a Mitzvah to respect his wishes.[3]]

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[1] Rama 344:10; Darkei Moshe 344; Maryu 4; Shut Ranach 50; Teshuvah Meahava 1:10, brought in Pischeiy Teshuvah 344:2; See Nitei Gavriel Vol. 2 1:7

Other opinions: Some Poskim rule one is to respect the wishes of the deceased and not keep the laws of Shiva or Aveilus. [Iyun Yaakov Sanhedrin 47 and Shvus Yaakov 2:102, brought in Pischeiy Teshuvah 344:2; Rav Akiva Eiger 344:10 questions ruling of Rama and argues that even Shiva and Shloshim don’t have to be kept per the request of the deceased. His reason is because in truth, whether Aveilus is on behalf of the dead or living is a dispute between the Rambam and Ramban, and we rule in 345 like the Rambam that it is on behalf of the dead, and hence can be nullified. He concludes with a Tzaruch Iyun Ledina.]

[2] The reason: As he does not have a right to nullify the entire laws of Aveilus. Likewise, perhaps the entire Takana of mourning is on behalf of the living, and hence the deceased has no jurisdiction over it. [Darkei Moshe ibid, brought in Rav Akiva Eiger 344-see there in length]

[3] Shach 344:9; Maryu ibid; Gilyon Maharsha Y.D. 240:9;  Nitei Gavriel Vol. 2 3:22