[fpc-other] Pascal interfaces is the same as multiple inheritance ?

[Andrey Gusev]

I wish to introduce some additional (and general) functional to an 
existing (and foreign) freepascal's unit.
With C++'s multiple inheritance quality it is easy to implement:
---
#include <stdio.h>
#include <list>

using namespace std;

class TObj {
protected:
	int fff;
};

class TObj2: TObj {
protected:
	int fff2;
};

class TIntf {
public:
	virtual void ppp() = 0;
};

class TObji: public TIntf,TObj {
public:
	virtual void ppp();
};

class TObj2i: public TObji,TObj2 {
public:
	virtual void ppp();
};

void TObji::ppp()
{
	printf("111 %p\n",this);
	fff = 111;
}

void TObj2i::ppp()
{
	printf("222 %p\n",this);
	fff2 = 222;
	TObji::ppp(); // like "inherited" in pascal
}

typedef list<TIntf*> myList;

int main(void)
{
	myList l;
	l.push_back(new TObji);
	l.push_back(new TObj2i);
	for (myList::iterator i = l.begin(); i != l.end(); ++i)
		(*i)->ppp(); // general interface used
}
---
TObj,TObj2 - the basic classes from foreign module
TObji,TObj2i - my additional functional implementation

But i can't invent nothing like that (except the some procedural hack 
with pointers substitution), in object pascal, with him interfaces!
Can somebody direct me to some object-style variant, maybe objfpc 
relieve here (now i use delphi mode) ?