For the first game of the triangular series Kallis changed his shirt number to 65, the age of his father Henry, who was recently diagnosed with lung cancer.
Kallis dedicated his hundred in that match against England at the Oval to his father and has continued to pile on the runs -- an unbeaten century against Zimbabwe the next day and a match winning 82 not out against England at Old Trafford on Thursday.
"Jacques is not one to give away much emotion but there are obviously difficulties back home -- he's very much in contact with his family," Boucher said on Friday.
"He's a very strong character and I know that he is doing this for a reason. When someone of that sort of class is going out there to score runs...watch out.
"I've watched Jacques play for some 300 games now. When Jacques Kallis hits form, if the hunger is there then he'll play like he is at the moment. The series we played against the West Indies (1998-1999) at home and now here -- they are probably the best I've seen him play."
SENIOR PLAYER
Boucher, a friend since they first started playing together, paid tribute to the way Kallis has assumed the role of senior player since the departure of players such as Jonty Rhodes, Allan Donald and Lance Klusener.
"I think he does have a big influence, more on the field than off. It would have done the world of good for someone like Jacques Rudolph to bat with him last (Thursday) night.
"There would have been times when Jacques Rudolph might have thought it was time to attack the spinners, or something like that, but a guy like Jacques Kallis would have gone up to him told him to bide his time."
South Africa lead the standings in the series after defeating England by seven wickets at Old Trafford, a result which Boucher said has given them renewed self-belief.
"We're very thrilled with the result last night, especially after what happened at the Oval. We went out yesterday knowing that we had to win -- for a lot of reasons," Boucher said.
South Africa lost by six wickets to England at the Oval last Saturday but then beat Zimbabwe by 46 runs in Canterbury on Sunday.
"We know we have to win one more game to get into the final. We are definitely starting to pick up some momentum now. There are still a few areas we can improve on -- I don't think our fielding was that great yesterday although the field was pretty wet," Boucher said.
South Africa play their next match against Zimbabwe in Cardiff on Saturday.
