No, not directly at least. The fact that they both have the D initial means they are both from the D clan, so they are related in that sense. However, luffy is not roger's son, or grandson or nephew or anything like that. Luffy's father is dragon.
Ace, born as Gol D. Ace and nicknamed "Fire Fist" Ace, was the sworn older brother of Luffy and Sabo, and the biological son of the late Pirate King, Gol D. Roger, and Portgas D. Rouge.
Ace was Dragon's son, Emporio Ivankov expected that Dragon would go to Marineford to save Ace, showing that Dragon holds love and care towards his family and possibly his son, Luffy, despite not being involved in his childhood.
Monkey D. DragonMonkey D. Luffy/Parents
Outlook IIIOutlook III, Sabo's father. Outlook III, Sabo's father is a stereotypical noble, treating Ace and Luffy as trash, and panicking about being contaminated when Bluejam got their blood onto him during a beating, claiming that he needed to be decontaminated.
BedMD: Foods That May Give You NightmaresCheese. Of the 68 participants who indicated that their dreams were affected by eating certain foods, 12.5 percent blamed it on cheese. Pasta. Don't tell your nonna — ragus, ziti and other such dishes nabbed 12.5 percent. Meat. Pizza. Spicy Foods. Pickles. Milk. Sugar, Sweets and Candy.
Sugar is also soluble in water, and also lowered the freezing/melting point of the water, but sugar does not make ice melt as fast as salt does. Flour does not cause the ice cube to melt faster because the flour has almost the same freezing/melting point as pure water.